If a population saves more money (that is the marginal propensity to save increases across all income levels), then total revenues for companies will decline. This decrease in economic growth means fewer salary increases and perhaps downsizing. Eventually the population's total savings will have remained the same or even declined because of lower incomes and a weaker economy. This paradox is based on the proposition, put forth in Keynesian economics, that many economic downturns are demand based.
Keynes himself notes the appearance of the paradox in The Fable of the Bees: or, Private Vices, Publick Benefits (1714) by Bernard Mandeville, the title itself hinting at the paradox, and Keynes citing the passage:
"As this prudent economy, which some people call Saving, is in private families the most certain method to increase an estate, so some imagine that, whether a country be barren or fruitful, the same method if generally pursued (which they think practicable) will have the same effect upon a whole nation, and that, for example, the English might be much richer than they are, if they would be as frugal as some of their neighbors. This, I think, is an